In the past a standard desktop microcomputer laid flat on
top of a desk and ran power form an electrical wall outlet. The monitor, or
display screen usually was placed on top of the horizontal desktop case. Today
this configuration of microcomputer has all but been replaced by the
minitower, (see below.)
A microcomputer with a tower case contains the same basic
computers as a standard desktop microcomputer, but the vertical-oriented case is
large and allows more room for expansion. The tower unit can be placed on the
floor to save space. IN the past the tower was usually used for a server, but
today most servers are mounted in racks and the tower is most often seen in a
smaller minitower configuration as a normal PC workstation.
Notebook or Laptop Microcomputer
A notebook computer is small and light, (about the size
of a notebook,) giving it the advantage of portability that
standard desktop computer do not have. Early notebook
computers were a littler larger and were called laptops.
That name is still used interchangeably with notebook.
A notebook computer can run on power from an electrical wall
outlet or on its own batteries. Today there are very small
notebook computers called mini-laptops.
Today there are very small handheld computers that
have evolved from the early personal data assistants, (PDAs).
A minicomputer (colloquially, mini) is a class of
multi-user computers that lies in the middle range of the
computing spectrum, in between the largest multi-user
systems (mainframe computers) and the smallest single-user
systems (microcomputers or personal computers). The class at
one time formed a distinct group with its own hardware and
operating systems, but the contemporary term for this class
of system is midrange computer, such as the higher-end
SPARC, POWER and Itanium -based systems from Sun
Microsystems, IBM and Hewlett-Packard.
Mainframes are large, fast and very expensive
computers, generally used by business or governments to
provide centralized storage, processing, and management of
large amounts of data. As with a minicomputer, one mainframe
computer carries out processing tasks for multiple users who
input processing requests using a terminal. However, a
mainframe generally services more users than a minicomputer.
To process large amounts of data, mainframes often include
more than one processing unit. One of these processing units
directs overall operations. A second processing unit handles
communication with all the users requesting data. A third
processing unit finds the data requested by users. Some
microcomputers that used for network servers now have
Mainframes remain the computer of choice in situations where
reliability, data security, and centralized control are
necessary. The price of a mainframe computer system is
typically several hundred thousand dollars. A mainframe
computer is housed in a closet-size cabinet and its
peripheral devices are contained in separate cabinets.
Supercomputers are the fastest and most expensive
type of computer. The cost of a supercomputer ranges from
$500,000 to $35 million or even more.
Originally designed for “computer-intensive” task such as
weather prediction, molecular modeling, and code-breaking,
supercomputers today have also expanded into business
markets where the sheer volume of data would cause lengthy
processing delays in a traditional mainframe environment.
For example, MCI uses supercomputer technology to manage a
huge pool of customer data. Queries that once took over two
hours, now take about a minute of supercomputer time.
The speed of a supercomputer can reach one trillion
instructions per second, making it possible to perform
complex tasks such as modeling the movement of thousands of
particles in a tornado or creating realistic animations.
In 1981 when the original IBM Personal Computer was announced,
IBM released three operating systems for it. How many of you remember that?
Since I wrote the first IBM course on how to fix this original PC, I had to know
at least a little about all three of them.
IBM decided early in the development process of the PC that they
did not want to hire a bunch of programmers to write software for it -
especially an operating system. IBM wanted the hardware business and did not
care about the software. Since there was no clear-cut contender for an operating
system at the time, IBM approached three organizations about writing one for the